1. Field of the Invention
The invention relates to an attachment to be used for towing a vehicle.
2. Background Art
When a disabled vehicle or a vehicle having undergone an accident is towed with a wrecker, front or rear wheels of the vehicle are raised, and the vehicle is towed with the other wheels rolling freely.
FIG. 5 is a schematic view showing that front wheels of a vehicle 101 to be towed (simply called a “towed vehicle 101”), such as a disabled vehicle or a vehicle having undergone an accident, are raised. As can be seen from the drawing, a T-shaped arm 102 is extended from a wrecker 100 toward the towed vehicle 101, and a lower portion of the towed vehicle 101 is retained with a vehicle towing attachment 103 fixed on the arm 102, thereby raising the front wheels.
FIG. 6 is a schematic representation showing the attachment 103. The attachment 103 is mounted on either end of the T-shaped arm 102. As shown in FIG. 6, the attachment 103 comprises two prongs 103a, 103b; and a recess 103c existing between the prongs 103a, 103b. 
FIG. 7 is a side view showing that the towed vehicle 101 is raised with the attachment 103. As shown in FIG. 7, for example, when the towed vehicle 101 is an automobile such as a truck, a center plate spring 104 is provided as a shock absorber for the front wheel 106. A forward fulcrum 104a of the plate spring 104 is supported on a frame 107. The attachment 103 is inserted from below to a position located rearward of the fulcrum 104a. The plate spring 104 is fitted between the prongs 103a, 103b, and the lower portion of the plate spring 104 is supported with the recess 103c, thus raising the front wheel 106.
However, when the towed vehicle 101 is towed by the wrecker 100, relative force acts between the towed vehicle 101 and the attachments 103 for various reasons, such as acceleration/deceleration, a directional change, or a deteriorated state of a road surface. At this time, the conventional attachments 103 shown in FIG. 6 fail to retain the towed vehicle 101 without fail.
Particularly, when force acts in the longitudinal direction of the plate spring 104 between the towed vehicle 101 and the attachments 103, there arises a problem of the attachments 103 sliding in the longitudinal direction of the plate springs 104. In this case, damage is inflicted on the plate springs 104 and the neighborhood thereof. In order to prevent occurrence of such damage, as shown in FIG. 7, the root of the arm 102 and the plate spring 104 must be bound together with a chain 105 while the plate springs 104 are held with the attachments 103. Therefore, very complicated operation is required at the time of towing operation.
The plate springs 104 deflect vertically according to a road condition during towing operation. For this reason, if the chain 105 is bound directly around the plate spring 104, the chain 105 will be bitten at the neighborhood of the fulcrum 104a. As a result, there arises a problem of the chain 105 being disabled or the plate spring 104 being subjected to damage.